1. Field of the Invention
The invention concerns an arrangement for the spectrally resolving detection of a sample, wherein the sample is illuminated by an illuminating radiation and wherein sample radiation emitted by the sample is detected, the arrangement comprising an illuminating beam path via which illuminating radiation can be delivered to the sample from an lighting source, and an observation beam path via which sample radiation can be delivered to a detector as observation radiation, wherein an interferometer, disposed in a section of the observation beam path which does not include the sample, splits incident interferometer input radiation into two portions by means of an interferometer beam splitter, directs the two radiation portions along two paths which are provided with radiation-guiding means and whose effective path length difference can be modified, and superimposes the two radiation portions in an mutually interfering manner so as to form an interferometer output radiation such that the spectral distribution of the observation radiation impinging at a specific point of the detector can be varied by varying the effective path length difference.
The invention further concerns a process for the spectrally resolving detection of a sample that is illuminated by means of an illuminating radiation by detecting a sample radiation emitted by the sample, in which illuminating radiation is supplied to the sample from a lighting source along an illuminating beam path, and sample radiation is provided to a detector as observation radiation along an observation beam path, wherein observation radiation passes through an interferometer that is disposed in a section of the observation beam path which does not comprise the sample, in which interferometer the observation radiation as incident interferometer input radiation is split into two radiation portions by means of an interferometer beam splitter, the two radiation portions are directed along two paths whose effective path length difference can be varied, and the two radiation portions are superimposed in a mutually interfering manner to form an interferometer output radiation, wherein sequentially a number of measurement data are recorded with various settings of the effective path length difference, so that the spectral distribution of the observation radiation impinging at one specific point of the detector is different for different measurements.
2. Description of Related Art
A device of this generic type and a process of this generic type are known from EP 0767361 A2. There is described an imaging spectrometer for the spectral analysis of light emitted from a sample. An interferometer is provided in the observation radiation beam path of a known spectrometer, in which interferometer light from one point in a focal plane of the sample is coupled-in as a parallel ray bundle with a particular angle of incidence. The input beam is split into two partial beams by means of a semi-transmissive (half-slivered) mirror functioning as a beam splitter. The partial beams follow different paths in the interferometer and are reunited at the outlet of the interferometer in a manner mutually interfering with each other. The reunited beam is imaged upon the sensitive surface of an image-generating detector. The paths, through which the two partial beams pass in the interferometer, exhibit relative to each other an optical (or more generally: an effective) path length difference (OPD: optical path difference). In the known array the optical path length difference corresponds substantially to the geometric path length difference. The OPD in the known interferometer is variable by changing the geometric light path. In equivalent manner, the index of refraction in the area of the light path could be varied.
For carrying out a spectral analysis, multiple recordings are made with a detector, wherein the OPD set in the interferometer is varied between the individual recordings. This has the consequence, that depending upon adjustment of the OPD certain spectral components of the observation radiation are amplified or, as the case may be, attenuated or cancelled by interference. The spectral distribution of the observation light impinging at one point of the detector is thus not only dependent upon the spectral distribution of the light emitted by the sample, but rather also by the respective adjusted OPD. Note, that the OPDs for different detector points, as a rule, are different. Each individual detector point can also be considered, independent from the remaining detector points, as a one channel single detector.
The result of a measurement of this type is a sequence of intensity measurement units as a function of the interferometer settings. The term “measurement units” refers in the one dimensional case to a single measurement value and signifies, in the case of an imaging spectrometer, a recorded individual image. The recorded sequence of intensity measurement units corresponds in the imaging case to an “image stack”, in which the same respective pixels along the axis of interferometer settings parameters (for example, an adjustment angle) correspond to each other and can be considered as unidimensional measurements of the corresponding sample point.